A New Tool for Conservation Genetics: Seal Placentas

It's a sad fact that as members of a species become rarer they tend to suffer from inbreeding. This lack of genetic diversity can lead to birth defects and other problems, making a species even more endangered as time progresses.

It’s a sad fact that as members of a species become rarer they tend to suffer from inbreeding. This lack of genetic diversity can lead to birth defects and other problems, making a species even more endangered as time progresses.

Conservationists regularly test the genetic makeup of many endangered species in order to understand the threats they face and, sometimes, to help them adapt to limited breeding choices. This isn’t always an easy task. Sometimes animals are so rare they’re hard to find in the wild, or the only evidence is hair or feces that may not contain a lot of DNA. Other times collecting a blood or tissue sample for DNA analysis can be dangerous, either to the researcher or the animal. After all, nobody likes to be tranquilized and then poked with a sharp needle.

So, how can conservationists collect DNA samples that will provide maximum information with the least amount of risk to the animals they’re studying? One word: placentas.

Yes, placentas. According to a study published this week in the Finnish journal Annales Zoologici Fennici, placentas can be a valuable source of genetic material that can help identify inbreeding and reveal other important data, such as the genders of the newborns.

The researchers, from several universities and institutions in Finland, tried this out with Saimaa ringed seals (Pusa hispida saimensis), one of the rarest seal species on the planet. Only about 300 of these critically endangered seals remain, all in a land-locked lake in that country, where they face constant pressure from fishermen and climate change, which has caused a high level of infant mortality from lack of ice.

Despite the low population, the seals continue to breed. According to the paper, between 50 and 60 seal pups are born every year. That means a fair number of placentas are left behind for potential testing.

Between 2009 and 2011 the researchers collected 59 placentas from the seals’ ice-bound birthing dens. Most of the placentas were already decomposing, but they still contained enough genetic material for testing. Each placenta offered multiple opportunities for genetic extraction: the uterine side of the placenta for DNA from the mothers and the fetal side and umbilical cord for DNA from the pups.

The researchers also had some actual seal DNA for comparison, but that’s the sad part of the story: the tissue mostly came from stillborn pups found at the birthing sites.

Testing the placentas revealed a lot about the pups’ genotypes, mostly that they exhibited the expected low levels of genetic diversity. The tests revealed nothing about the mothers, nor did they conclusively indicate which pups were siblings (probably because their genetics overlapped so much).

The researchers wrote that this test is the first to prove that placentas have value in genetic monitoring. They added that although the test didn’t yield a huge amount of data, more advanced genetic sequencing tests, coming in the near future, may reveal even more. And this technique could play an especially important role in Saimaa ringed seal conservation because while collecting samples from the “elusive and difficult to capture” wild animals is almost impossible, gathering placentas is relatively easy.

Of course this approach can’t work with every species. Pinnipeds (seals) are one of the few groups that don’t regularly eat their own placentas, so samples might be unavailable for other animals. There are, however, a lot of endangered seal species worldwide, and the researchers predict that the placental testing technique could prove valuable for several of them. It’s one more tool in conservation biologists’ pockets that could help save critically endangered, inbred species from extinction.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

ABOUT THE AUTHOR(S)

John R. Platt

John R. Platt is the editor of The Revelator. An award-winning environmental journalist, his work has appeared in Scientific American, Audubon, Motherboard, and numerous other magazines and publications. His "Extinction Countdown" column has run continuously since 2004 and has covered news and science related to more than 1,000 endangered species. John lives on the outskirts of Portland, Ore., where he finds himself surrounded by animals and cartoonists.

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